1. Field of the Invention:
This invention relates to a semiconductor laser array device which oscillates high output power laser lights with a 0.degree.-phase shift therebetween.
2. Description of the Prior Art:
Semiconductor laser devices having a single lasing filament structure can only produce 50-80 mW lights at best. In order to produce high output power, semiconductor laser devices, in which a plurality of lasing filaments are disposed in a parallel manner on the same substrate to achieve an optical phase coupling between the adjacent lasing filaments, have been studied.
In the case where a plurality of index-guided semiconductor laser devices are disposed in a parallel manner with an optical phase coupling between the adjacent lasing filaments and the individual laser devices have the same gain, they tend to oscillate laser lights with a 180.degree.-phase shift therebetween rather than with a 0.degree.-phase shift therebetween. This is because, in the 180.degree.-phase shift mode, the electric field in the center area between the adjacent lasing filaments is zero while the electric field in the center area of each of the lasing filaments exhibits the maximum value, so that the electric field distribution is in accord with the gain distribution in the 180.degree.-phase shift mode rather than in the 0.degree.-phase shift mode, resulting in high oscillation gain.
The far-field pattern of laser lights with a 0.degree.-phase shift therebetween exhibits a single peak so that the laser lights can be concentrated into a spot by means of optical lenses, whereas the far-field pattern of laser lights with a 180.degree.-phase shift therebetween exhibits dual peaks so that the laser lights cannot be concentrated into a spot by any optical lens. These semiconductor laser array devices producing laser lights which cannot be concentrated into a spot are inconvenient in an optical coupling with other optical systems, and cannot be used as light sources for optical communication. Thus, creation of a semiconductor laser array device oscillating laser lights with a 0.degree.-phase shift therebetween (i.e., attaining higher oscillation gain in the 0.degree.-phase shift mode than in the 180.degree.-phase shift mode), which can thereby be utilized as a light source for optical communication, is required.